CVE-2025-5868 is a critical vulnerability identified in RT-Thread version 5.1.0, specifically within the sys_thread_sigprocmask function located in the rt-thread/components/lwp/lwp_syscall.c source file. The vulnerability arises due to improper validation of an array index derived from the manipulation of the 'how' argument. This improper validation can lead to out-of-bounds access or memory corruption, potentially allowing an attacker with limited privileges (low privileges required) to compromise the confidentiality, integrity, and availability of the affected system. RT-Thread is a widely used real-time operating system (RTOS) designed for embedded systems, IoT devices, and industrial control systems. The vulnerability’s CVSS 4.0 base score is 8.6, indicating a high severity level. The attack vector is adjacent network (AV:A), meaning exploitation requires network proximity but not direct local access. The attack complexity is low (AC:L), no user interaction is needed (UI:N), and no authentication is required (AT:N). The vulnerability impacts all three security properties (confidentiality, integrity, availability) at a high level, making it a critical concern for embedded devices relying on RT-Thread 5.1.0. Although no known exploits are currently in the wild, the potential for exploitation exists due to the ease of triggering the improper validation. The lack of available patches at the time of publication increases the urgency for affected organizations to implement mitigations or upgrade once fixes are released.

For European organizations, the impact of CVE-2025-5868 can be significant, especially those operating in sectors heavily reliant on embedded systems and IoT devices such as manufacturing, automotive, healthcare, and critical infrastructure. Exploitation could lead to unauthorized control over embedded devices, disruption of industrial processes, leakage of sensitive operational data, or denial of service conditions. Given the increasing adoption of RT-Thread in smart devices and industrial control systems across Europe, successful exploitation could result in operational downtime, safety hazards, and financial losses. Furthermore, compromised devices could be leveraged as footholds for lateral movement within corporate networks, increasing the risk of broader cyberattacks. The vulnerability’s exploitation via adjacent network access means attackers could be insiders or positioned within the same network segment, raising concerns for organizations with less segmented or poorly secured internal networks.

To mitigate CVE-2025-5868, European organizations should: 1) Immediately identify and inventory all devices running RT-Thread 5.1.0 within their environment. 2) Monitor vendor communications closely for patches or updates addressing this vulnerability and apply them promptly once available. 3) Implement network segmentation to isolate embedded and IoT devices from critical network assets, limiting the attack surface and reducing the risk of lateral movement. 4) Employ strict access controls and network filtering to restrict adjacent network access to vulnerable devices, including the use of firewalls and VLANs. 5) Conduct regular security assessments and penetration testing focused on embedded systems to detect exploitation attempts. 6) Where possible, consider upgrading to newer, patched versions of RT-Thread or alternative RTOS solutions with better security track records. 7) Deploy runtime protections such as memory protection units (MPUs) or intrusion detection systems tailored for embedded environments to detect anomalous behavior indicative of exploitation attempts.